Revamp wasi example and related docs

[ifsheldon]

Closes #9777

For now, this is a draft PR because there's a runtime issue in the revamp example. Please see the FIXME in examples/wasi/main.rs. There I want to invoke the exported wasi:cli/[email protected] function, which is the main function in examples/wasi/wasm/wasi.rs. Probably @alexcrichton or @fitzgen can help a bit? Thanks!

When the runtime issue is fixed, I will try to revamp more sections in the related doc in following commits

Updated:

This PR revamps the examples wasi and wasi-async with latest updates from wasmtime and wasmtime-wasi and uses WASIp2 APIs by default. Related documentation is also updated.

[ifsheldon]

But now there comes another issue: this hello-world example is just too specific to wasi:cli, since we used a specific wasmtime_wasi::bindings::sync::Command to run a wasi:cli/command. For a more general component, we need to add another example or at least give a pointer.

BTW, I still don't know why I could not get a Func to execute the run function in wasi:cli/run.

[alexcrichton]

Personally I think it's reasonable to start with hello-world like this and then graduate up to other examples. For example this page could link to the bindgen_examples page and that could get expanded with a custom world for example (IIRC there may already be one there?)

BTW, I still don't know why I could not get a Func to execute the run function in wasi:cli/run.

You needed another invocation of get_export. You loaded the exported instance but you'll need to load the exported function of that instance as well.

[ifsheldon]

OK, I think this draft PR seems good to me now, so I turned it into a formal PR.

[ifsheldon]

You needed another invocation of get_export. You loaded the exported instance but you'll need to load the exported function of that instance as well.

OK, got that. I also added related code in the example to demonstrate how to do that.

BTW, do you know why ComponentNamedList is implemented for tuple (A1,) but not A1? Should I file another issue for this? This is bit counter-intuitive when I want to write something like func.typed::<(), Result<(), ()>>(&store), which rustc complains about not implementing ComponentNamedList. I really didn't know how to fix this error until I lookup Implementations on Foreign Types section of ComponentNamedList.

[alexcrichton]

Thanks!

This is bit counter-intuitive when I want to write something like func.typed::<(), Result<(), ()>>(&store),

This is currently intentional in the sense that it's in theory preferred to use the output of bindgen! where you don't have to deal with this. In that sense the raw component APIs weren't designed to be the most ergonomic and easy-to-use since that's where bindgen! comes in to close the gap.

IIRC there were coherence with that trait impl, but I could be misremembering as well.

[ifsheldon]

Oops. CI complains about file not found target/wasm32-wasip2/debug/wasi.wasm, so I guess CMakeLists also needs to be updated.

Furthermore, I digged into examples/wasi/main.c and related c-api crate. It seems c-api crate also needs some renovation.........

For example, c-api exposes this function, which links wasip1 interfaces, but no other functions link wasip2 interfaces.

wasmtime/crates/c-api/src/linker.rs

Line 111 in db4bd21

pub extern "C" fn wasmtime_linker_define_wasi(

I think removing preview1 feature from this line and fixing whatever breaks should be enough. This introduces API breaking changes, though.

wasmtime/crates/c-api/Cargo.toml

Line 36 in db4bd21

wasmtime-wasi = { workspace = true, optional = true, features = ["preview1"] }

I'd rather like to skip this error first and open another tracking issue.

[ifsheldon]

Can you take a look at the CI error Test C-API macos-latest? I think I made a right correction on CMakeList.txt but I don't know what else needs to be fixed.

[alexcrichton]

Have you tried running the example locally?

[ifsheldon]

For the C example, inside examples, I ran mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-wasi and then cd ../.. && ./examples/build/wasmtime-wasi and it worked. The C example still runs the old wasip1 module though, as I mentioned c-api crates lacks wasip2 support now. Revamping C wasi example is blocked until #8036 is resolved by #9812 etc.

[alexcrichton]

Ah I better understand what was going on now. Instead of replacing the current example which I think is still useful for wasm32-wasip1 targets, could this perhaps rename the prior wasi example to wasip1 and add this new example under wasip2? There then wouldn't be a C example of wasip2 because that's not supported yet.

[ifsheldon]

OK, I've brought back wasip1 examples.

[ifsheldon]

This test failure is weird to me. I have cleaned all caches and run the commands in this test manually on my Mac but I saw no failures.